1. Field of the Invention
The present invention relates to a three dimensional projection system, and more particularly to a three dimensional projection system in which image adjusting operation as well as focus regulating operation for obtaining an image on a screen could be performed simultaneously by operating a pair of projecting lenses integrally by using a single driving motor, thereby removing a keystoning phenomenon.
2. Description of the Prior Art
There are various kinds of three dimensional color projection systems and/or display systems. One peculiar approach has two projectors or display systems, where one projector provides a right eye display and the other a left eye display on a screen. Each display has its own polarization, for instance, "P" and "S", respectively. The viewer wears polarized spectacles which let the eyes see a stereoscopic display for three dimensional viewing.
Generally, a stereoscopic apparatus is used for accomplishing the above-mentioned three dimensional display. This apparatus includes a pair of projecting units which are provided in front of the screen while keeping at a predetermined distance. Two projecting units project the same object so that their picturing angles are different from each other on the screen to overlap thereon and the overlapped images are perceived by the eyes through the polarized glasses for three dimensional viewing.
However, in such a kind of three dimensional projection system utilizing the two-beam separating method, if the distance between the screen and each of projecting unit and/or the distance between the projecting units, are not adjusted exactly, the two projected images through each of the projecting unit will be out of focus so that a misoverlapped image is formed on the screen, or so that a complete image is not formed on the screen.
FIG. 1 is a schematic constitution view for showing the above-mentioned conventional three dimensional projection system. It will be described in detail below.
The conventional three dimensional projection system mainly has first and second projecting units 1a and 1b, each of which provides a left eye display and a right eye display. In detail, the first and second projecting units respectively include a first and a second light source 4a and 4b, respectively, such as xenon lamps, first and second spherical reflecting mirrors 3a and 3b for reflecting the light emitted to the backward direction from the light sources, first and second collimating lenses 5a and 5b for condensing the emitting light as well as the reflected light from the spherical reflecting mirrors to transform the lights into parallel lights, first and second LCD (liquid crystal display) panels 6a and 6b (or a first and a second slide films), and first and second projecting lenses 7a and 7b. An observer perceives the projected image as a stereoscopic display through polarization spectacles 8.
In the above-mentioned three dimensional projection system, each of the projecting unit is controlled in order to accord the image and to adjust the focus. That is, in case that the images respectively projected from the projecting units onto a screen S1 are not accorded, and in case that the focusing is not adjusted because the distances between the projecting units and the screen are inaccurate, the projecting units are moved with respect to each other to complement the deviation by adjusting the projecting direction as well as a projecting angle.
Therefore, there are problems in that the adjusting operation is exceedingly troublesome and inconvenient. Furthermore, only a specialist can accomplish an exact adjusting operation because the adjusting operation should be performed by manual operation while staring at the images on screen S1.
In addition, in the above-mentioned three dimensional projection system, because light axes of the projecting units La and Lb are inclined at a predetermined angle with respect to a central axis of the screen L1, the distances from projecting lenses 7a and 7b to both left and right sides of screen S1 are different. Thus, the magnifying proportion of the images on the left side of the screen is different from that on the right side of the screen. As a result, as shown in FIG. 7A, there is a problem in that the two images are projected as a trapezoid in the vertical direction to not completely coincide with each other.
Such an appearance is called a keystoning phenomenon by which the screen is distorted (referring to FIG. 7A). If the keystoning phenomenon occurs, the observer's feeling of satisfaction is reduced and the fatigue of the observer's eyes is aggravated.
U.S. Pat. No. 5,125,733 (issued to Lee) discloses an apparatus for integrally operating a pair of projecting lenses in order to settle the above-mentioned problems. In this apparatus, the light axes of projecting objects, the light axes of projecting lenses, and the central axis of the screen are parallel to each other to accord two images projected onto the screen, thereby preventing the keystoning phenomenon.
As per the above-mentioned apparatus, an excellent image without trapezoidal distortion can be obtained. However, the construction of the apparatus is complicated and manufacturing thereof is difficult.